Brake disc with symmetric groove pattern

ABSTRACT

A brake disc for a wheeled vehicle; said brake disc including opposing annular braking surfaces; each of said surfaces provided with an identical pattern of disparate arcuate groove segments; said groove segments arranged in groups oriented in both clockwise and anti-clockwise directions; each of said groups including, one series of at least two arcuate groove segments lying along a common are extending from proximate a hub of said braking surface to proximate the periphery of said braking surface, one inward arcuate groove segment extending from proximate said hub to a point intermediate said hub and said periphery, and one outward arcuate groove segment extending from a point intermediate said hub and said periphery to proximate said periphery.

RELATED APPLICATION

This application is a continuation of application Ser. No. 15/094,268filed on Apr. 8, 2016, which is a continuation of application Ser. No.13/997,028 filed on Aug. 7, 2013, which is a 371 of InternationalApplication PCT/AU2011/001660 filed on Dec. 22, 2011, which designatedthe U.S., the entire contents of each of which are incorporated hereinby reference.

The present invention relates to discs for vehicle brakes and, moreparticularly, to groove segments provided in the braking surfaces ofsuch discs.

BACKGROUND

Many arrangements of groove segments on the braking surfaces of thebrake discs of vehicles are known. One such is that disclosed forexample in U.S. Pat. No. 7,097,006, which itself references a largenumber of groove arrangements.

Groove segments are aids, in heat dissipation, stress relief andvibration reduction, and need to be tailored to the particularcharacteristics and construction of the disc to which they are applied.

A difficulty has been to derive a pattern of groove segments which meetsthese requirements but is also effective in a disc rotating in eitherclockwise or anti-clockwise directions so that the disc may be used oneither side of a vehicle and provide balanced and equal brakingperformances regardless of the direction of rotation.

Furthermore, the configuration of the actual machined slot hasimplications for both the performance of the brake pads applied to thedisc surfaces and the integrity of the disc itself. Thus some known slotconfigurations at least, have either a tendency to tearing of the rotorsurfaces or to cause hairline crack development at the brake bandperipheries, or both.

Another problem with conventional brake discs is that there is no way amotorist can monitor the braking performance of the braking assembly ofthe vehicle. Braking efficiency and problems of incompatibility betweenbrake pads and the brake bands of the disc can be indicated by thetemperature of the discs after heavy braking, but this temperature canonly be ascertained by use of sophisticated thermal monitoringequipment.

It is an object of the present invention to address or at leastameliorate some of the above disadvantages.

Notes

The term “comprising” (and grammatical variations thereof) is used inthis specification in the inclusive sense of “having” or “including”,and not in the exclusive sense of “consisting only of”.

The above discussion of the prior art in the Background of theinvention, is not an admission that any information discussed therein iscitable prior art or part of the common general knowledge of personsskilled in the art in any country.

In this specification:

-   -   “Arcuate groove” means a groove following an arc of a circle or        other geometrically defined curve.    -   “Clockwise” and “anti-clockwise” refer to rotational directions        about the centre of a brake disc as viewed from the outward        side.

BRIEF DESCRIPTION OF INVENTION

Accordingly, in a first broad form of the invention, there is provide abrake disc for a wheeled vehicle; said brake disc including opposingannular braking surfaces; each of said surfaces provided with anidentical pattern of disparate arcuate groove segments; said groovesegments arranged in groups, each group including at least:

-   (a) a pair of inner arcuate groove segments extending outwardly from    proximate an inner circumferential edge of a said brake band surface    to proximate a mid portion of the width of said brake band,-   (b) a pair of outer arcuate groove segments extending outwardly from    proximate a mid portion of the width of said brake band to proximate    an outer circumferential edge of said brake band, and    wherein said pair of inner arcuate groove segments and said pair of    outer arcuate groove segments each include a clockwise arcing and an    anticlockwise arcing groove segment; said brake disc providing    identical braking performance independent of direction of rotation.

Preferably, each of said opposing braking surfaces includes four of saidgroups of arcuate groove segments; each said group occupying a quadrantof said brake disc.

Preferably, respective said clockwise arcing groove segment andanticlockwise arcing groove segment of each of said pair of innerarcuate groove segments and said pair of outer arcuate groove segmentsare disposed symmetrically about respective radial lines of symmetry.

Preferably, said clockwise arcing groove segment of said pair of outergroove segments is located along an are defining said clockwise arcinggroove segment of said pair of inner arcuate groove segments; said outergroove segment separated from said inner groove segment by a gap.

Preferably, said of each said arcuate groove segments arcs outwardlyconvexly.

Preferably, said pattern includes a pair of intermediate arcuate groovesegments; said pair of intermediate arcuate groove segments disposedsymmetrically about a radial line of symmetry.

Preferably, an anticlockwise arcing one of said pair of intermediatearcuate groove segments is located such that its midpoint lies on saidare defining said clockwise arcing groove segment of said pair of innerarcuate groove segments and at a midpoint of said gap separating saidouter groove segment from said inner groove segment.

Preferably, a said radial line of symmetry of said pair of outer arcuategroove segments lies approximately 15 degrees advanced in a clockwisedirection from a radial line of symmetry of said pair of inner arcuategroove segments.

Preferably, a said radial line of symmetry of said pair of outer arcuategroove segments lies approximately 30 degrees advanced from a radialline of symmetry of said pair of inner arcuate groove segments.

Preferably, a said radial line of symmetry of said pair of intermediatearcuate groove segments lies approximately midway between said radiallines of symmetry of said pair of inner arcuate line segments and saidpair of outer arcuate line segments.

Preferably, said pair of inner arcuate groove segments is machined suchthat end portions of said groove segments adjacent an innercircumferential edge of said brake band surface gradually increase indepth.

Preferably, said pair of outer arcuate groove segments is machined suchthat end portion of said groove segments adjacent an outercircumferential edge of said brake band surface gradually increase indepth.

Preferably, distal ends of said pairs of inner and outer arcuate groovesegments are machined such that said grooves are at full depth at saiddistal ends.

Preferably, both ends of said intermediate pairs of arcuate groovesegments are machined such that said grooves are at full depth at saidboth ends.

Preferably, outer rims of brake bands forming said opposing annularbraking surfaces are provided with at least one set of colour markings;said colour markings applied with thermally sensitive paints.

Preferably, said colour markings comprise stripes of said thermallysensitive paints extending from an edge of an inward facing said annularbraking surface of an inner said brake band to an edge of an outwardfacing said annular braking surface of an outer said brake band.

Preferably, said stripes are of distinct colours; each said distinctcolour changing colour according to a predetermined elevated temperatureband.

In another broad form of the invention, there is provided a method ofproviding equal braking performance in a brake disc for a vehicle inboth clockwise and anticlockwise rotation; said method including thesteps of machining a repeating groove pattern in surfaces of opposingbrake bands of said disc; each, of said repeating groove patternsincluding at least a pair of inner arcuate groove segments and a pair ofouter arcuate groove segments; a first arcuate groove segment of eachsaid pair arcing towards a mid portion of a said brake band in aclockwise direction; a second arcuate groove segment of each said pairarcing to wards a mid portion of a said brake band in an anticlockwisedirection.

Preferably, ends of said inner and outer arcuate groove segmentsadjacent respective inner and outer peripheries of said brake bandsurfaces are machined so as to gradually reach full depth as machiningproceeds away from said inner and outer peripheries.

Preferably, distal ends of said inner and outer arcuate groove segmentsare machined such that said groove segments remain at said full depth atsaid distal ends.

In yet another broad form of the invention, there is provided a patternof grooves provided in opposing annular brake band surfaces of a discbrake disc; said pattern comprising three sets of arcuate groovesarranged radially around each of said opposing brake band surfaces; eachset of said three sets of arcuate grooves including four pairs ofradially distributed arcuate grooves, grooves of each said pair ofarcuate grooves extending symmetrically in clockwise and anticlockwisedirections about a respective radial line of four radial lines of saidset; said four radial lines defining four equal annular portions of saidbrake band surface.

Preferably, grooves of said first set arc convexly from an innerperiphery of a said brake band to at least a mid portion of said brakeband surface.

Preferably, said four radial lines for said second set of arcuategrooves are rotationally offset in a clockwise direction relativeorientation of said four radial lines for said first set of arcuategrooves; said rotational offset approximately 30 degrees; said offsetsuch that each said arcuate groove of said second set lies substantiallyon a continuation of an arc defined by a corresponding arcuate groove ofsaid first set.

Preferably, grooves of said second set arc convexly from an outerperiphery of a said brake band towards respective outer ends of saidarcuate grooves of said first set; each respective outer end of anarcuate groove of said second set separated from a corresponding outerend of a corresponding arcuate groove of said first set by a gap.

Preferably, said four radial lines for said third set of arcuate groovesare rotationally offset in an anticlockwise direction relativeorientation of said four radial lines for said first set of arcuategrooves; said rotational offset approximately 30 degrees; said offsetsuch that each said arcuate groove of said third set extends throughsaid gap between outer ends of corresponding arcuate grooves of saidfirst set and said second set; midpoints of said arcuate grooves of saidthird set proximate said arcs defined by arcuate grooves of said firstset.

Preferably, each said arcuate groove of said third set arcs convexlyfrom a first end proximate a mid portion of said brake band surface to asecond end towards an outer periphery of said brake band.

Preferably, said first ends of said arcuate grooves of said third setlie at a smaller radial distance from a centre of said disc than aradial distance of outer ends of said arcuate grooves of said first set.

Preferably, said second ends of said arcuate grooves of said third setlie at a greater radial distance from said centre of said disc than aradial distance of outer ends of said arcuate grooves of said secondset.

In another broad form of the invention, there is provided a brake discfor a wheeled vehicle; said brake disc including opposing annularbraking surfaces; each of said surfaces provided with an identicalpattern of disparate arcuate groove segments; said groove segmentsarranged in groups; each group including at least:

-   -   (a) a pair of inner arcuate groove segments extending outwardly        from proximate an inner circumferential edge of a said brake        band surface to proximate a mid portion of the width of said        brake band,    -   (b) a pair of outer arcuate groove segments extending outwardly        from proximate a mid portion of the width of said brake band to        proximate an outer circumferential edge of said brake band, and        wherein said pair of inner arcuate groove segments and said pair        of outer arcuate groove segments each include a clockwise arcing        and an anticlockwise arcing groove segment; said brake disc        providing identical braking performance independent of direction        of rotation; said brake disc further provided with at least one        set of temperature sensitive coloured markings at the periphery        of said brake disc; respective ones of said coloured markings        changing colour at a predetermined band of elevated temperature        of said brake disc.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the present invention will now be described withreference to the accompanying drawings wherein:

FIG. 1 is an orthogonal side view of one side a brake disc provided withpatterns of arcuate groove segments according to a first preferredembodiment of the invention,

FIG. 2 is a perspective view of the brake disc of FIG. 1,

FIG. 3 is an orthogonal side view of one side of a brake disc providedwith patterns of arcuate groove segments according to a second preferredembodiment of the invention,

FIG. 4 is a perspective view of the brake disc FIG. 3,

FIG. 5 is a partial cross section of the brake disc of FIG. 1 and FIG. 3showing the machining pattern of groove segments adjacent the innerperipheries of the brake band surfaces,

FIG. 6 is a partial cross section of the brake disc of FIG. 1 and FIG. 3showing the machining pattern of groove segments adjacent the outerperiphery of the brake band surfaces and groove segments at anintermediate position.

FIG. 7 is a view of a first set of groove segments forming a part of thegroove pattern of the second preferred embodiment of the invention,

FIG. 8 is a view of a second set of groove segments forming a part ofthe groove pattern of the second preferred embodiment of the invention,

FIG. 9 is a view of a third set of groove segments forming a part of thegroove pattern of the second preferred embodiment of the invention,

FIG. 10 shows the complete pattern of groove segments according to thesecond preferred embodiment of the invention as formed by thecombination of the sets of groove segments of FIGS. 7 to 9,

FIG. 11 is a general perspective view of brake disc according to theinvention showing thermal indicating markings on outer rims of the brakebands of the brake discs in a further preferred embodiment of theinvention,

FIG. 12 is an enlarged view of a set of the thermal markings of FIG. 11.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS First Preferred Embodiment

With reference to FIGS. 1 and 2, a brake disc 10 comprises opposingannular brake bands 12 and 14 supported by a central hub 16. Brake bands12 and 14 may form the outer surfaces of a solid disc or, as shown inFIG. 2, comprise two discs interconnected by arrays of pillars 18 whichallow air flow between the brake bands, as well known in the art.

Each outer surface 20 and 22 of the brake bands 12 and 14 is providedwith groups 24 of arcuate groove segments 26, machined into therespective outer surfaces. Preferably, the groove segments 26 areapproximately 3 mm in width with a depth of approximately 1.5 mm.

The following description refers to the surface 20 of brake band 12 asshown in FIG. 1, but it will be understood that the identicalarrangement of groove segments is applied to the surface 22 of theopposite brake band 14. Preferably the patterns on the two opposingsides are rotationally offset by 30 degrees.

Each group 24 of arcuate groove segments 26 of this preferred embodimentof the invention, comprises arcuate groove segments oriented in bothclockwise and anti-clockwise directions. The groups are four in numberand occupy 90 degree quadrants of the brake band surface 20.

Each group includes one pair of inner arcuate groove segments 27 and 28,extending outwardly from proximate the inner circumferential edge 30 ofthe brake band surface 20, across approximately three quarters of thewidth, or at least past the mid portion, of the brake band. Groovesegments 27 and 28 are disposed about a radial line of symmetry. 32, andarc convexly in opposing clockwise and anticlockwise directions, withtheir inner termini 34 and 36 adjacent the radial line of symmetry 32.

Each of the groove segments 27 and 28 is associated with one of a pairof outer shorter arcuate groove segments, 38 and 40 respectively. Thefirst of these, shorter groove segment 38, extends outwardly fromproximate the mid portion of the width of the brake band surface 20 andarcs, also convexly, in a clockwise direction to a point at theperiphery 42 of the brake band surface 20, and proximate the radial lineof symmetry 32 of groove segments 27 and 28.

The second shorter groove segment 40 is equal in extent to the firstshorter groove segment 38, but arcs convexly in the oppositeanticlockwise direction. The two shorter groove segments 38 and 40 aresymmetrical about a radial line of symmetry 44 advanced approximately 15degrees in a clockwise direction from the radial line of symmetry 32 ofthe pair of inner groove segments 27 and 28.

This pattern of groove segments 26 is repeated for each quadrant of thebrake bands 12 and 14.

Second Preferred Embodiment

In a second preferred embodiment of the invention and with reference nowto FIGS. 3 and 4, a similar brake disc 100 as previously described aboveis similarly provided with an arrangement of groove segments 226,identical on each opposing brake band 212 and 214.

The groove segments 226 are arranged also in four repeating groups 224of groove segments; each group 224 thus occupying a 90 degree quadrantof a brake band surface 220 and 222. For convenience of description,each quadrant may be divided into three sectors of approximately 30degrees. Each group 224 includes a pair of innermost groove segments 227and 228 disposed symmetrically about a first 30 degree radial line ofsymmetry 232, and have their inner termini 234 and 236 adjacent theinner circumferential edge 230 of the brake band. These inner groovesegments extend outwardly, convexly clockwise and anticlockwiserespectively, to approximately three quarters of the width of the brakeband surface 220.

In this embodiment, the pattern also includes a pair of clockwise andanticlockwise outer groove segments 238 and 240 respectively,symmetrical about the second 30 degree radial line of symmetry 244. Thepreferred arrangement is such that the first of these outer groovesegments, the clockwise groove segment 238, lies on the arc of clockwiseinner groove segment 227, being separated from the distal end of thatgroove segment by a gap 235. Each of these outer groove segments 238 and240 extends approximately the outer one third of the width of the brakeband, with their distal termini proximate the outer periphery 242 of thebrake band surface 220.

Each quadrant 224 includes one further pair of clockwise andanticlockwise intermediate groove segments 246 and 248 respectively.Intermediate groove segments 246 and 248 are disposed symmetricallyabout a radial line of symmetry 250 lying approximately midway betweenthe lines of symmetry 232 and 244 of the pairs of inner and outer groovesegments respectively. The arrangement is such that the anticlockwiseintermediate groove segment 246 passes through the gap 235 and such thatits midpoint lies on the arc defining the previously described innergroove segment 227 and outer groove segment 238.

It can be seen that each of the embodiments described above provides foran equal number and total lengths of clockwise and anticlockwise arcuategroove segments on each brake band of the brake disc. This allows thediscs to be equally effective in braking regardless of the direction ofrotation of the disc.

The pattern of arcuate grooves of this second embodiment, mayalternatively be described as a combination of the patterns of threesets of grooves. With reference to FIGS. 7 to 9, each of the three setscan be described with reference to four radial lines (100, 102, 104 and106) (with specific relative orientation for each set) which define fourequal annular portions of the brake band surface (120); that isadjoining pairs of these four radial lines subtend right angles.

Each of the three sets of arcuate grooves comprises four pairs ofgrooves, in which each pair comprises a clockwise groove and ananticlockwise groove arranged symmetrically about a radial line.

With reference now to FIGS. 7 and 10, in the first set of the three setsof arcuate grooves, each pair of arcuate grooves (127, 128) arc convexly(clockwise and anticlockwise) from proximate an inner periphery (130) ofthe brake band to outer ends (135, 137), somewhat past a mid portion ofthe brake band surface (120).

As can be seen in Figures s and 10, the four radial lines for the secondset of pairs of arcuate grooves (138, 139) are rotationally offset in aclockwise direction relative the orientation of the four radial linesfor the first set of arcuate grooves. This rotational offset isapproximately 28 degrees, and is such that each clockwise arcuate grooveof this second set lies substantially on a continuation of an arcdefined by a corresponding clockwise arcuate groove of the first set, ascan be seen in FIGS. 3 and 10.

The pairs of arcuate grooves (138, 139) of the second set arc convexlyfrom proximate the outer periphery (142) of the brake band, towards therespective outer ends (135, 137) of the arcuate grooves (127, 128) ofthe first set. The respective outer ends (151, 153) of the arcuategrooves (138, 139) of this second set are separated from thecorresponding outer ends (135, 137) of the first set by gaps (135) ascan be seen in FIGS. 3 and 10.

With reference now to FIGS. 9 and 10, the four radial lines (100, 102,104 and 106) for the third set of pairs of arcuate grooves (146, 148)are rotationally offset in an anticlockwise direction relative to theiroriginal orientation for the first set of arcuate grooves (127, 128) asshown in FIG. 7. In this case the rotational offset is approximately 28degrees, with the offset such that each of the anticlockwise arcuategroove of the pair of grooves (146, 148) of this third set extendsthrough a gap (135) between the outer ends of corresponding arcuategrooves of the first set (127, 128) and the second set (138, 139). Themidpoints of these arcuate grooves (146, 148) of the third set lieapproximately on the arcs defined by the arcuate grooves (127; 128) ofthe first set. Each pair of arcuate grooves (146, 148) of the third setarcs convexly from first ends (155, 157) proximate a mid portion of saidbrake band surface, to second ends (161, 163) towards the outerperiphery (242) of the brake band.

FIG. 10 shows the three sets of arcuate grooves combined now to form thecomplete pattern of grooves on the brake band surface.

It can be seen that the grooves of the three sets are arranged so thatthere is at least some overlap of the grooves. That is, there is noannular band of the surface of the brake bands which is not interruptedby the grooves of at least one of the sets of grooves. Thus the firstends (155, 157) of the arcuate grooves of the third set lie at a smallerradial distance from the centre of the disc than the radial distance ofouter ends (135, 137) of the arcuate grooves (127, 128) of said firstset, so that these ends overlap radially.

Similarly, the second ends (161, 163) of the arcuate grooves (146, 148)of the third set, lie at a greater radial distance from the centre ofthe disc than the radial distance of the outer ends (151, 153) of thearcuate grooves (138, 139) of the second set, again providing anoverlap.

Third Preferred Embodiment

In a further preferred embodiment according to the invention, the brakerotor brake bands and grooving conforms to the that described in eitherof the above first and second embodiments. In this preferred embodimenthowever, the outer rims (300, 302) of the brake bands are provided withat least one set (304) of colour markings as indicated in FIG. 10.

Preferably, each set (304) of the at least one set, comprises a paintedstripe extending transversely from the edge of the outward facingsurface of the outer brake band (302) to the edge of the inward facingsurface of the inner brake band (300).

Preferably also, the sets (304) of colour markings are regularlyarranged around the circumference of the brake disc and are sufficientin number such that at least one set will be visible to an observerregardless of the position the brake disc has assumed when the vehicleto which it is fitted has come to rest.

In a preferred arrangement as shown in FIG. 12, each set (304) iscomprised of three spaced apart painted stripes (306), (308) and (310).The colours are distinct one from the other so as to be readilydistinguishable and are preferably green, orange and red with all thesets repeating the pattern of colours in the same order.

The paints used for the stripes (306,308,310) are thermally sensitivepaints which react to elevated temperatures in the metal to which theyhave been applied and react by changing to different colours when thetemperature of the supporting surface reaches predetermined elevatedtemperature bands.

Preferably, in the present embodiment of the invention, the green paintof stripe (306) changes to white in the temperature band of 458° C. to856° C., the orange stripe (308) changes to yellow between 550° C. and1022° C., while the red stripe (310) also changes to white between 630°C. and 1166° C.

The brake disc of the present embodiment is supplied together with acolour interpretation chart (not shown) so that the vehicle owner oroperator can refer to the chart and compare the current colour of thestripes with that of the chart. The chart may additionally containinformation as to possible interpretations of the current colour of adisc under different braking conditions as an aid to assessing brakingperformance.

Groove Machining

In each of the above embodiments, the arcuate groove segments aremachined in a particular way. Typically grooves machined in discsurfaces are introduced into the disc material by a gradual plunging ofthe ball cutter tool as it is moves along the trajectory of the groovepath, and exits in a similar way by gradually retracting the tool tip asit approaches the end of the groove path.

In grooves which end at some intermediate point on the disc brake band,that is in the area of maximum applied force by the brake callipers,such “feathered” groove ends tend to react adversely with the brake pad,in some cases causing a tearing of the disc material. Nevertheless,feathered or gradually produced groove ends are advantageous for thosegroove ends close to either the outer or inner peripheries of the brakeband, in that they reduce the possibility of hair line fracturesdeveloping between the groove end and the disc periphery. These areasclose to the inner and outer peripheries of the brake band surface arein any case not swept by the brake pads.

It can be seen, particularly in FIGS. 5 and 6, that the grooves of thepresent invention retain the advantages of feathered ends 50 of grooveends at both the inner periphery 30 and the outer periphery 42 (inFIG. 1) and feathered ends 254 of groove ends at both the inner andouter peripheries 230 and 242 (in FIG. 3). However the distal ends (52and 252 respectively) of these grooves are not feathered. Nor are bothends of the intermediate grooves 246 and 248 so feathered.

In both embodiments of the invention, the preferred machining method forgroove ends adjacent to the brake band surface peripheries, is togradually introduce the tool tip (preferably an 80 degree 5 mm ballcutter) into the disc material as the tool moves away from the peripheryalong the groove path until the required depth is reached, then machinein towards the middle portion of the brake band. When the distal end ofthe groove path is reached, tool motion parallel to the disc surface isarrested and the tool withdrawn from the groove. Preferably, the ballcutter is plunged into the disc surface to a maximum depth at which thegroove width at the surface is 3 mm.

The grooves machined in this way thus have full groove depthsubstantially up to the ends (52/252) of the grooves in the middleportion of the brake bands, and tests have indicated that this grooveend configuration eliminates the problem of disc material tearing. Atthe same time the method retains the advantages associated with afeathered groove end configuration at the brake band peripheries.

In the case of the Second Preferred Embodiment, the pair of intermediatearcuate groove segments 246 and 248 are machined such that the groovesare of the same depth throughout. These groove segments are machined byplunging the tool tip to the full depth of the groove at the start ofthe groove and retracting the tool tip at the end of the groove afterthe tool tip motion parallel to the brake surface has been arrested.

Test have further shown that the arrangement of groove segmentsdescribed in each of the embodiments, provides for excellent brakingperformance as well as providing the major benefit of equal performanceregardless of direction of rotation.

The above describes only some embodiments of the present invention andmodifications, obvious to those skilled in the art, can be made theretowithout departing from the scope of the present invention.

The invention claimed is:
 1. A brake disc for a wheeled vehicle; saidbrake disc including opposing annular braking surfaces; each of saidsurfaces provided with an identical pattern of disparate arcuate groovesegments; said groove segments arranged in groups; each group includingat least: (a) a pair of inner arcuate groove segments extendingoutwardly from proximate an inner circumferential edge of a said brakeband surface to proximate a mid portion of the width of said brake band,(b) a pair of outer arcuate groove segments extending outwardly fromproximate a mid portion of the width of said brake band to proximate anouter circumferential edge of said brake band, wherein said pair ofinner arcuate groove segments and said pair of outer arcuate groovesegments each include a clockwise arcing and an anticlockwise arcinggroove segment; said brake disc providing identical braking performanceindependent of direction of rotation, and wherein each of the innerarcuate groove segments and each of the outer arcuate groove segmentscomprises a first end and a second end, and wherein each of therespective inner and outer arcuate groove segments arcs outwardlyconvexly along an entire length of the respective inner and outerarcuate groove segments from the first end to the second end.
 2. Thebrake disc of claim 1, wherein each of said opposing braking surfacesincludes four of said groups of arcuate groove segments; each said groupoccupying a quadrant of said brake disc.
 3. The brake disc of claim 1,wherein respective said clockwise arcing groove segment andanticlockwise arcing groove segment of each of said pair of innerarcuate groove segments and said pair of outer arcuate groove segmentsare disposed symmetrically about respective radial lines of symmetry. 4.The brake disc of claim 1, wherein said pattern includes a pair ofintermediate arcuate groove segments; said pair of intermediate arcuategroove segments disposed symmetrically about a radial line of symmetry.5. The brake disc of claim 1, wherein said pair of inner arcuate groovesegments is machined such that end portions of said groove segmentsadjacent an inner circumferential edge of said brake band surfacegradually increase in depth.
 6. The brake disc of claim 1, wherein saidpair of outer arcuate groove segments is machined such that end portionof said groove segments adjacent an outer circumferential edge of saidbrake band surface gradually increase in depth.
 7. The brake disc ofclaim 1, wherein distal ends of said pairs of inner and outer arcuategroove segments are machined such that said grooves are at full depth atsaid distal ends.
 8. A brake disc for a wheeled vehicle; said brake discincluding opposing annular braking surfaces; each of said surfacesprovided with an identical pattern of disparate arcuate groove segments;said groove segments arranged in groups; each group including at least:(a) a pair of inner arcuate groove segments extending outwardly fromproximate an inner circumferential edge of a said brake band surface toproximate a mid portion of the width of said brake band, (b) a pair ofouter arcuate groove segments extending outwardly from proximate a midportion of the width of said brake band to proximate an outercircumferential edge of said brake band, wherein said pair of innerarcuate groove segments and said pair of outer arcuate groove segmentseach include a clockwise arcing and an anticlockwise arcing groovesegment; said brake disc providing identical braking performanceindependent of direction of rotation, and wherein said clockwise arcinggroove segment of said pair of outer groove segments is located along anarc defining said clockwise arcing groove segment of said pair of innerarcuate groove segments; said outer groove segment separated from saidinner groove segment by a gap.
 9. The brake disc of claim 8, whereineach of said arcuate groove segments arcs outwardly convexly.
 10. Abrake disc for a wheeled vehicle; said brake disc including opposingannular braking surfaces; each of said surfaces provided with anidentical pattern of disparate arcuate groove segments; said groovesegments arranged in groups; each group including at least: (a) a pairof inner arcuate groove segments extending outwardly from proximate aninner circumferential edge of a said brake band surface to proximate amid portion of the width of said brake band, (b) a pair of outer arcuategroove segments extending outwardly from proximate a mid portion of thewidth of said brake band to proximate an outer circumferential edge ofsaid brake band, wherein said pair of inner arcuate groove segments andsaid pair of outer arcuate groove segments each include a clockwisearcing and an anticlockwise arcing groove segment; said brake discproviding identical braking performance independent of direction ofrotation, and wherein an anticlockwise arcing one of said pair ofintermediate arcuate groove segments is located such that its midpointlies on said arc defining said clockwise arcing groove segment of saidpair of inner arcuate groove segments and at a midpoint of said gapseparating said outer groove segment from said inner groove segment. 11.The brake disc of claim 10, wherein each of the inner arcuate groovesegments and each of the outer arcuate groove segments comprises a firstend and a second end, and wherein each of the respective inner and outerarcuate groove segments arcs outwardly convexly along an entire lengthof the respective inner and outer arcuate groove segments from the firstend to the second end.